Dead battery

that pic is a very old schematic. voltage regulators have been internal since the 80's.
the pic also mentions alternator/generator. probably dates that pic to the mid 50's.
before. cars were 6 volts positive ground. with generators.
then they became 12 volts negative grounded with alternators and external regulators.

and today's alternator puts out 150 amps. now granted you will see a voltage climb after startup but that's to be expected since you drained the battery a little for cranking the motor up. but generally, 14 volts will be seen at an idle. raising the idle does no good on todays vehicles.

so when you got 10 volts. battery dead. you will see a SLOW climb. and when you got 4 batteries at 1000 amps a peace. well, 4000 amps is gonna take some time to gain voltage.

and on a another note. acid turns to water as the battery drains down.

a battery that is fully charged has a freeze point of -52. the lower the charge, the highter the water content. the higher the freeze point.

a battery that is only 25 percent charged has a freeze point of 20 degrees.

and for the guy that said pull the air filter for a shot of ether. NOT necessary. your creating more work then needed just for a shot of ether.
the motor has to suck in air. filter or no filter. ether will get sucked in with the air. and ether doesn't ruin the filter.

 

Takes 10 minutes. I've done it a few times. No problems.

 

So if my truck is showing 13.7-9 while driving, 14.00-1 while idling, its good?

 

I wouldn't worry. Those numbers look ok.

 

jump it with a car and it overloads the alternator. sooner or later you will burn up that car alternator.

 

if you have good cables it can be done given enough time, it wont hurt your car battery if done properly (leave the car on).